That doesn't make sense. There isn't a dedicated light for the logo in any of Apple's laptops -- what you see is the LCD backlight shining through a cutout in the case. This has been the case ever since they started doing that with the Powerbook G3 (iirc).
The logo was translucent and also allowed light in from the back. There was a logo-shaped burn issue but it was caused by ambient light shining through the logo. At least that's how I understood it.
+1. I can imagine someone leaving the laptop in full sunlight, and it burning through the logo - but it feels more like user issue, you don't leave electronics out like that.
